> On 8 Sep 2026, at 16:03, Richard Biener <[email protected]> wrote:
>
> On Tue, 8 Sep 2026, Kyrylo Tkachov wrote:
>
>>
>>
>>> On 8 Sep 2026, at 15:21, Richard Biener <[email protected]> wrote:
>>>
>>> On Mon, 7 Sep 2026, [email protected] wrote:
>>>
>>>> From: Kyrylo Tkachov <[email protected]>
>>>>
>>>> genmatch can leave the iterators of a named match unexpanded. Code
>>>> generation
>>>> emits COND_EXPR conditions in opcode switches. Overlapping delayed
>>>> iterator
>>>> sets can then emit duplicate case labels.
>>>
>>> Can you show an example pattern?
>>
>> Patch 3/3 is enabled by this. I want to write:
>> (for cmp (ge gt)
>> (match (unsigned_integer_sat_add @0 @1)
>> (cond^ (cmp:c (bit_not @1) @0)
>> (plus:c @0 @1) integer_minus_onep)))
>>
>> (for cmp (lt le)
>> (match (unsigned_integer_sat_add @0 @1)
>> (cond^ (cmp:c (bit_not @1) @0)
>> integer_minus_onep (plus:c @0 @1))))
>>
>> The :c modifier also generates the comparison with swapped operands:
>> • (ge gt) produces direct GE/GT and commuted LE/LT.
>> • (lt le) produces direct LT/LE and commuted GT/GE.
>>
>> Without this patch genmatch emits this:
>
> Hmm. But it seems this is maybe an unfortunate interaction
> between for substitution delaying and :c lowering? That is,
> how is this special to (cond ...)? It seems to me the
> real issue is elsewhere (some sorting issue?)
>
Perhaps. Tbh I was just trying to unblock patch 3 so I went with a localized
small fix, but I can look to see if this should a more general fix.
Thanks,
Kyrill
> On a related note it seems that lower_cond should no longer
> be necessary -- there is no GENERIC comparison operator
> in [VEC_]COND_EXPR anymore.
>
> Richard.
>
>> switch (gimple_assign_rhs_code (_a2))
>> {
>> case GE_EXPR:
>> case GT_EXPR:
>> { ... }
>>
>> case LE_EXPR:
>> case LT_EXPR:
>> { ... }
>>
>> case LT_EXPR: /* Duplicate. */
>> case LE_EXPR: /* Duplicate. */
>> { ... }
>>
>> case GT_EXPR: /* Duplicate. */
>> case GE_EXPR: /* Duplicate. */
>> { ... }
>> }
>>
>> Thanks,
>> Kyrill
>>
>>>
>>>> Substitute a group before decision-tree insertion when one of its iterators
>>>> occurs in a COND_EXPR condition. The existing eager path keeps the
>>>> substitutions aligned and lets the decision tree merge common concrete
>>>> operations. Other named matches keep delayed substitution.
>>>>
>>>> A reduced GIMPLE and GENERIC matcher with overlapping iterator sets fails
>>>> to
>>>> compile before this change. Both forms compile after the change.
>>>> This is needed to accept the patterns in patch 3/3.
>>>>
>>>> Bootstrapped and tested on aarch64-none-linux-gnu.
>>>>
>>>> Ok for trunk?
>>>> Thanks,
>>>> Kyrill
>>>>
>>>> gcc/ChangeLog:
>>>>
>>>> * genmatch.cc (cond_expr_condition_contains_id): New function.
>>>> (lower_for): Expand iterators used in COND_EXPR conditions.
>>>> (lower): Update comment.
>>>>
>>>> Signed-off-by: Kyrylo Tkachov <[email protected]>
>>>> ---
>>>> gcc/genmatch.cc | 44 ++++++++++++++++++++++++++++++++++++++++----
>>>> 1 file changed, 40 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/gcc/genmatch.cc b/gcc/genmatch.cc
>>>> index 1bc5875d7dd..c4bb1c12400 100644
>>>> --- a/gcc/genmatch.cc
>>>> +++ b/gcc/genmatch.cc
>>>> @@ -2159,6 +2159,26 @@ contains_id (operand *o, user_id *id)
>>>> return false;
>>>> }
>>>>
>>>> +/* Return true if O contains a COND_EXPR condition that refers to ID. */
>>>> +
>>>> +static bool
>>>> +cond_expr_condition_contains_id (operand *o, user_id *id)
>>>> +{
>>>> + if (capture *c = dyn_cast <capture *> (o))
>>>> + return c->what && cond_expr_condition_contains_id (c->what, id);
>>>> +
>>>> + if (expr *e = dyn_cast <expr *> (o))
>>>> + {
>>>> + if (*e->operation == COND_EXPR && contains_id (e->ops[0], id))
>>>> + return true;
>>>> + for (unsigned i = 0; i < e->ops.length (); ++i)
>>>> + if (cond_expr_condition_contains_id (e->ops[i], id))
>>>> + return true;
>>>> + }
>>>> +
>>>> + return false;
>>>> +}
>>>> +
>>>>
>>>> /* In AST operand O replace operator ID with operator WITH. */
>>>>
>>>> @@ -2304,9 +2324,24 @@ lower_for (simplify *sin, vec<simplify *>&
>>>> simplifiers)
>>>> else
>>>> can_delay_subst = false;
>>>> }
>>>> - if (sin->kind == simplify::MATCH
>>>> - && can_delay_subst)
>>>> - continue;
>>>> + /* Code generation emits COND_EXPR conditions in opcode switches.
>>>> + Substitute iterators in these conditions before inserting the patterns
>>>> + into the decision tree. Overlapping iterator sets could otherwise
>>>> + emit duplicate case labels. */
>>>> + if (sin->kind == simplify::MATCH && can_delay_subst)
>>>> + {
>>>> + for (unsigned si = worklist_start;
>>>> + si < worklist.length () && can_delay_subst; ++si)
>>>> + for (unsigned i = 0; i < n_ids; ++i)
>>>> + if (cond_expr_condition_contains_id (worklist[si]->match,
>>>> + ids[i]))
>>>> + {
>>>> + can_delay_subst = false;
>>>> + break;
>>>> + }
>>>> + if (can_delay_subst)
>>>> + continue;
>>>> + }
>>>>
>>>> unsigned worklist_end = worklist.length ();
>>>> for (unsigned si = worklist_start; si < worklist_end; ++si)
>>>> @@ -2374,7 +2409,8 @@ lower (vec<simplify *>& simplifiers, bool gimple)
>>>> /* Lower for needs to happen before lowering cond
>>>> to support (for cnd (cond vec_cond)). This is
>>>> safe as substitution delay does not happen for
>>>> - cond or vec_cond. */
>>>> + cond or vec_cond, or for iterators used in a
>>>> + COND_EXPR condition. */
>>>> out_simplifiers.truncate (0);
>>>> for (auto s: simplifiers)
>>>> lower_for (s, out_simplifiers);
>>>>
>>>
>>> --
>>> Richard Biener <[email protected]>
>>> SUSE Software Solutions Germany GmbH,
>>> Frankenstrasse 146, 90461 Nuernberg, Germany;
>>> GF: Jochen Jaser, Andrew McDonald, Abhinav Puri; (HRB 36809, AG Nuernberg)
>>
>>
>>
>
> --
> Richard Biener <[email protected]>
> SUSE Software Solutions Germany GmbH,
> Frankenstrasse 146, 90461 Nuernberg, Germany;
> GF: Jochen Jaser, Andrew McDonald, Abhinav Puri; (HRB 36809, AG Nuernberg)
